A movable reflective element capable of tilting a reflective surface is used as an element for controlling the direction of light beams or directional radio waves. Particularly, the movable reflective element capable of tilting the reflective surface with two axes of freedom is used as an installed component of a two-dimensional scanner for two-dimensional scanning of light beams or the like. The two-dimensional scanner for scanning light beams two-dimensionally using the movable reflective element is installed in, for example, a projector for projecting an image. The two-dimensional scanner for scanning directional radio waves two-dimensionally using the movable reflective element is installed in, for example, an onboard radar.
Recently, use of a micro-electro-mechanical system (MEMS) element that can be fabricated using semiconductor fabrication processes has been proposed for the movable reflective element. For example, Patent Literature 1 discloses a movable reflective element including outer actuators extending from inner sides of a fixed frame to a rotation axis of a movable frame, and inner actuators extending from the movable frame to a rotation axis (perpendicular to the rotation axis of the movable frame) of a mirror. The movable frame is oscillated by the outer actuators about one rotation axis at a low frequency (horizontal scanning frequency), while the mirror is oscillated by the inner actuators about the other rotation axis at a high frequency (vertical scanning frequency). Use of such a movable reflective element enables light reflected by the mirror to be scanned two-dimensionally in the horizontal and vertical directions.